Integrated circuits have increasing component densities as new generations of products are developed. The increased component density is generally achieved by reducing the size of the components within the integrated circuit. Typically, contact openings and other portions of the device are shrunk making some metal interconnections difficult to be formed. In doing so, interconnecting layers generally require a barrier that typically includes a refractory metal, refractory metal silicide, or refractory metal nitride. Compared to aluminum, these refractory metal materials typically are harder meaning that they are not elastic and do not easily bend.
FIG. 1 includes a plan view of a bond pad structure. The structure includes a scribe line 10, a conductive member 12 that includes an interconnect 122 and a bond pad 124. Overlying the interconnect 122 and a portion of the bond pad 124 is a passivation layer 16. The passivation layer is patterned such that it ends at the scribe line. The passivation layer also includes an opening 14 that exposes almost all of the bond pad 124. A wire 18 is bonded to the bond pad 124 at the bond pad opening 14. When bonding is performed, a foot 182 is formed within the wire 18.
FIG. 2 includes a cross-sectional view of the structure to illustrate problems that can arise during the wire bonding operation. The passivation layer 16 includes portions 162 and 164. Portion 162 lies along the surface of a substrate 20, and portion 164 lies over and along side the bond pad 124. Substrate 20 typically includes an insulating layer that contacts barrier layer 126. The bond pad 124 in this particular embodiment includes the barrier layer 126, a metallic layer 127, and an antireflective coating 128. The barrier layer 126 may also include an adhesion layer immediately adjacent to the surface of the substrate 20.
During one type of the wire bonding operation, the wire is moved laterally as indicated by the arrows in FIG. 2 to remove any native oxide that lies on layer 127 prior to wire bonding operation. This abrasion portion of the wire bonding step causes fractures to form in the passivation layer between portions 162 and 164. A fracture 21 is formed at a point in the passivation layer 16 where portions 162 and 164 meet. In some instances, portion 164 is completely ripped off the bond pad.
After the bond is formed, the bond pad 124 can lift because fracture 21 is formed. The lifting force typically occurs when the wire 18 reels out of a bonder after the wire 18 is bonded to the bond pad 124 and before bonding the wire to a post of a lead frame (not illustrated in FIGS. 1 and 2) or during a bond pull test. The lifting force can cause the fracture 21 to propagate along interface 22 or within barrier layer 126. If this occurs, the bond pad 124 is lifted at least partially away from the substrate 20. If there is an adhesion layer between the substrate 20 and the barrier layer 126, the separation occurs on either side or through an adhesion layer. The lifting phenomenon occurs because the barrier layer 126 is harder than the metallic layer 127. The integrated circuit is nonfunctional if the bond pad is lifted partly or completely away from the device.
After fracture 21 is formed, contaminants including water, hydrogen, mobile ions, or the like migrate between the passivation portion 162 and bond pad 124 and into the substrate 20. Bond pad lifting and contamination cause reliability problems and cannot be tolerated with semiconductor devices.